Visual observations of liquid filler metal flow within braze gap

Abstract

An in situ visualisation technique has been developed to observe liquid metal flow through a controlled gap. The technique can image and measure brazing filler metal flow velocities, positions, contact angles, and fillet shape. The system captures the two-dimensional fluid flow kinetics common in most capillary driven processes. It consists of a fully integrated, digital, closed loop heating station and a high speed digital camera. The apparatus provides an accessible approach for gathering dynamic braze wetting and flow data that are normally difficult to obtain in a furnace environment. Braze flow displacement curves are generated from the processed camera images. The flow data are being used to calibrate and validate a braze flow model that will predict the effects of dissolution, diffusion, compositional changes, and solidification on capillary fill and fillet geometry.